Robot arm



FIG. 1 is a perspective view of a robot arm;

FIG. 2 is a front elevational view thereof,

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a right-side elevational view thereof;

FIG. 5 is a left-side elevational view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken lines that are immediately adjacent to the shaded areas and define unshaded regions, represent the bounds of the claimed design. The broken lines that are shown within the broken line boundaries and the broken lines outside of the claim are directed to environment. The broken lines form no part of the claimed design. 

CLAIM The ornamental design for a robot arm, as shown and described. 